Method for producing cellulose derivatives

ABSTRACT

Samples of commercial cellulose having high crystallinity (&gt;80%) and a degree of polymerization of approximately 1500 were pretreated enzymatically under various conditions with commercial endoglucanases, before the chemical conversion to substituted cellulose derivatives was carried out. The enzymatically pretreated cellulose samples exhibited a significantly higher substitution, up to 222% higher, in comparison with control samples which had been treated with buffer without enzyme. The increase in substitution during the chemical reaction could be observed in the presence of various amounts of alkali, but fell as the amounts of alkali decreased. At the same degree of substitution of the cellulose derivative, the use of cellulose pretreated with endoglucanase significantly reduced the amount of alkali required by 60%, as compared with the use of cellulose pretreated only with buffer. Furthermore, by reducing the amount of water used in the reaction mixture in the chemical reaction, it was possible further to increase the substitution of enzymatically pretreated cellulose.

The present invention relates to a process for the preparation ofcellulose derivatives using cellulose pretreated with endoglucanases.

A reduction in the amount of alkali to be used by using cellulases in anenzymatic pretreatment stage has been described by Michels and Meister(DE 4 440 245 C1). Cellulases are enzyme complexes in which enzymeshaving different catalytic activities are combined: endoglucanases (EC3.2.1.4), exoglucanases, which are also known as cellobiohydrolases (EC3.2.1.74, EC 3.2.1.91) and β-glucosidases (EC 3.2.1.21). Those enzymeactivities together decompose cellulose completely to glucose, whereaseach on its own catalyses only partial steps of the decomposition.Endoglucanases, for example, cleave only endogenous β-1,4-glycosidicbonds in the amorphous regions of the polymer.

Surprisingly, endoglucanases can also be used alone in a similarpretreatment step for reducing the amount of alkali required. Moreover,the use of endoglucanases offers two important advantages in comparisonwith cellulases. Firstly, pretreatment with cellulases leads to aconsiderable loss of cellulose substrate to a marked reduction in thedegree of polymerisation (DP value) and to a loss of cellulosesubstrate. Secondly, the cellulase activity is inhibited by solubleoligomeric decomposition products, which considerably restricts thepossibility of the repeated use of a cellulase solution. That differencecan be attributed to the different catalytic activities of the twoenzymes.

Accordingly, the invention relates to a process by means of whichcellulose of a suitable commercial quality is pretreated withendoglucanases prior to chemical conversion to commercial cellulosederivatives. With the aid of that pretreatment process, the degree ofalkalisation of the cellulose and hence also the amount of chemicalsused in the after-treatment steps can be reduced considerably. Theprocess comprises treating the cellulose enzymatically withendoglucanases before it is introduced into the industrial manufacturingprocess. The cellulose pretreated in that manner and separated from theenzyme solution is hereinafter referred to as "activated". The cellulosederivatives prepared by the chemical conversion of activated celluloseare comparable with today's industrially manufactured products.

According to the invention, the process is as follows:

(A) A known weight of cellulose is pretreated with endoglucanase byincubation at a certain temperature and for a certain period of time ina suitable buffer system.

(B) The pretreated cellulose is then separated from the pretreatmentmixture consisting of the buffer and the enzyme.

(C) The "activated" cellulose is then reacted chemically as underindustrial conditions, but substantially less alkali is required for thereaction.

The conditions for the enzymatic pretreatment in step (A) can be variedas desired. Factors that affect the enzymatic pretreatment are:

(a) The origin of the endoglucanases, which originate from fungi,bacteria and plants, preferably from the fungi Trichoderma reesei,Humicola insolens and bacteria of the genera Bacillus, Cellulomonas,Sporocytophaga, Cytophaga, Clostridium. The use of Denimax Ultra L®(Novo Nordisk) is especially preferred.

(b) Buffer concentration from 1 to 1000 mM, preferred range from 10 to100 mM, especially preferred range 50 mM sodium acetate or potassiumphosphate according to the required buffer range. Other buffers orbuffer/solvent mixtures are also in accordance with the invention.

(c) pH value of the buffer in the range from pH 1 to pH 13, preferredrange from pH 4 to pH 10, especially preferred range from pH 5 to pH7.5.

(d) Ratio of the weight of the cellulose to the volume of the bufferfrom 1 g:0.5 ml to 1 g:1000 ml, preferably from 1 g:5 ml to 1 g:100 ml,especially from 1 g:10 ml to 1 g:30 ml.

(e) Ratio of the weight of the enzyme to the weight of the cellulosefrom 0.01 to 50%, preferred range from 1 to 30%, especially preferredrange from 3 to 12%.

(f) Incubation temperature from 0 to 100° C., preferred range from 20 to80° C., especially preferred range from 50 to 60° C.

(g) Incubation time from a few minutes to several days, preferred rangefrom 1 to 24 hours, especially preferred range from 2 to 3 hours.

(h) Shaking or stirring of the incubation mixture at from 1 to 10,000rpm, preferred range from 10 to 2000 rpm, especially preferred rangefrom 200 to 300 rpm.

The effect of those factors on the enzyme activity is known per se.Moreover, it has been shown that the cellulolytic enzymes obtained fromvarious species have different degrees of affinity and activity.Changing those factors in the pretreatment process will, therefore,affect the activation of the cellulose. That in turn leads to changes inthe degree of substitution of the chemically reacted cellulosederivatives.

The effects of the enzymatic pretreatment on the substitution values ofchemically reacted cellulose can be demonstrated in two different ways.Firstly, the enzymatically pretreated cellulose has significantly highervalues for the molecular substitution (MS) as compared with untreatedcontrols. Secondly, the amount of alkali required for the chemicalconversion reactions was significantly smaller when pretreated cellulosewas used. The invention therefore has the advantage of reducing theamount of alkali required for the conversion process and neverthelessyielding the same end product. Moreover, the use of endoglucanases inthe pretreatment stage offers two important advantages over cellulases:

The following interrelationships are shown in the Figures:

Pretreatment with Cellulase® led to a significant loss of material,which could be recognised by a reduction in weight and the fall in theDP value. The endoglucanases studied, on the other hand, exhibited onlya negligible loss of cellulose (FIGS. 1 and 3). The loss of material wasdue to the decomposition of the cellulose to soluble monomeric andoligomeric products in step (A), a loss of very fine particles in theseparation in step (B) and a loss of material on transfer to thechemical reaction vessels in (B/C). After 20 hours' incubation at atemperature of 36° C. and a buffer pH of 5, the cellulose studiedexhibited a gradual loss of material of up to 19% of the initial weight,depending on the enzyme concentration.

By contrast, the endoglucanases caused a negligible weight loss (FIG.1). Incubation of cellulose with a Cellulase® concentration of 2% (w/wenzyme weight to cellulose weight) under optimum conditions, that is tosay pH 5.5 and 50° C., likewise resulted in a gradual loss of materialof approximately 6% after an incubation period of 180 minutes. Cellulosesamples with a concentration of 6% and 15% (v/w--enzyme volume tocellulose weight) of the endoglucanase Denimax Ultra L® exhibited anegligible loss of material after the same incubation time at theoptimum pH of 7 and a temperature of 60° C. A concentration of 6%Cellusoft Ultra L® resulted in a negligible loss of material after 90minutes at pH 5.5 and 50° C.; thereafter there was an almost exponentialloss of cellulose material to approximately 5% after 180 minutes (FIG.3).

The cellulase activity is inhibited by the soluble oligomericdecomposition products. Consequently, the use of the buffer/cellulasemixture after separation of the pretreated cellulose in step (B) islimited. The absence of dissolved decomposition products and theirinhibiting effect on the endoglucanases means that thebuffer/endoglucanase mixture can readily be used again for pretreatingfurther cellulose samples, as a result of which material costs arereduced. As well as demonstrating the decomposition activity of theenzymes used in the Examples below, the curves are also important forcalculating standardised pretreated sample weights. After pretreatment,the same equivalent dry weights of cellulose material were thus presentfor each sample and were exposed to the same chemical conversionconditions.

FIG. 2 shows the changes in the degree of polymerisation (DP) forcellulose samples pretreated with different concentrations of cellulaseand endoglucanases in accordance with the description relating toFIG. 1. The degree of polymerisation fell as the enzyme concentrationincreased, so that maximum differences of approximately 13% and 15% weredetermined for samples pretreated with Denimax Ultra L® and Cellulase® .The Cellusoft Ultra L® samples exhibited a slightly higher endo-activitywith a 20% reduction as compared with the samples without enzymaticpretreatment. A similar trend was observed for the samples pretreatedunder optimum conditions (FIG. 4). In those cases, the reduction in thedegree of polymerisation, less than 10% in each case, was not lower.

Enzymatic pretreatment of the cellulose had a marked effect on thedegree of substitution of the cellulose derivatives which wereetherified by propylene oxide in an alkaline medium to formhydroxypropylcellulose (HPC) (FIG. 5). During incubation only in buffer(enzyme content=0%), degrees of substitution of from 0.4 to 0.5 mol %were achieved. The endoglucanases (Denimax Ultra L® and Cellusoft UltraL®) exhibited the same effectiveness as the cellulase. The change in thesubstitution in dependence on the enzyme concentration was characterisedin all tested enzymes by the occurrence of optima.

FIG. 6 shows the effects of alkali on the substitution values of thecellulose derivatives after the chemical reaction. Increasing amounts ofNaOH gave maximum MS values of 1.1 mol % in cellulose pretreated onlywith buffer. By pretreatment with the endoglucanase Denimax Ultra L, MSvalues of up to 2 mol % could be achieved. The effect of the enzymaticactivation appeared most clearly after a chemical reaction in thepresence of from 1.2 to 1.6 g of NaOH per g of cellulose. Denimax UltraL was used in an amount of 15% v/w and the reaction was carried out at200 rpm. Under those conditions, approximately 28% less NaOH wasrequired to prepare HPC having a degree of substitution of 1.0 afterenzymatic pretreatment.

In the samples containing enzymatically pretreated cellulose assubstrate, the degree of substitution can be increased still further byreducing the water content in the reaction mixture. Cellulose sampleswere pretreated by incubation for a period of 2 hours at 60° C., withvigorous shaking (200 rpm), in water, buffer and buffer containingenzyme (FIG. 7). After the incubation, the samples were filtered underslight pressure. The water retention values for the cellulose samplesvaried according to the filtration time and pressure. However, therelative water retention values between the various treatment methodsremained the same. This shows that under the test conditions chosenhere, although the enzymatic pretreatment changes the cellulosestructure, it does not bring about any significant change in the waterretention capability. However, the chemical conversion of those samplesso pretreated exhibited marked differences in the degree of molarsubstitution of their derivatives. The derivatives prepared fromenzymatically pretreated cellulose exhibited degrees of substitutionwhich were up to 91% higher as compared with cellulose samples which hadnot been treated enzymatically. That increase could be raisedsignificantly to 161% by optimising the water content in the reactionmixture.

FIG. 7 also shows the effect of the water involved in the reaction onthe synthesis of the derivatives. In the case of cellulose samplespretreated by incubation in water, the synthesised derivatives had amaximum molecular substitution of 0.8 with a water content of 3.1 g per1 g of cellulose. Samples pretreated with buffer possessed a similarwater content optimum with a slightly higher molecular substitution ofapproximately 0.88. As the water content fell, the samples pretreatedwith buffer exhibited increasingly higher MS values than samples treatedwith water. In contrast, derivatives synthesised from enzymaticallypretreated samples exhibited higher MS values at all the water contentsstudied, with a maximum MS value of 2.35 at 1.45 g of water per 1 g ofcellulose. Therefore, the enzymatically pretreated cellulose samplesused as substrates for the chemical conversion required approximately47% less water in order to achieve, as compared with samples which hadnot been treated enzymatically, a maximum MS value higher by 161%.

DESCRIPTION OF THE FIGURES

FIG. 1 Loss of cellulose material under the action of commercialcellulolytic enzymes. Cellulase® from Merck (), endoglucanases--DenimaxUltra L® (□) and Cellusoft Ultra L® (∇) from Novo Nordisk. 1.5 g samplesof Temming T 500 linters were shaken (200 rpm) at 36° C. and incubatedfor 20 hours with various enzyme concentrations. The Cellulase® andCellusoft Ultra L® samples were incubated in 50 mM sodium acetate bufferhaving a pH value of 5, and the Denimax Ultra L® samples were incubatedin 50 mM potassium phosphate buffer having a pH value of 7.1. After theincubation, the samples were cooled in an ice bath, filtered and washedunder slight pressure. The wet weights of the pretreated cellulosematerial were measured and the samples were dried in a vacuum oven at65° C. for 24 hours. Before the dry weights were determined, the sampleswere cooled to room temperature. The losses of material were given as apercentage of the initial weights.

FIG. 2 Change in the degree of polymerisation of the cellulose under theaction of commercial cellulolytic enzymes. Cellulose samples weredecomposed in the presence of various concentrations of the enzymesCellulase® (), Denimax Ultra L® (□) and Cellusoft Ultra L® (∇)according to FIG. 1; the samples were analysed and their respectivedegrees of polymerisation were determined.

FIG. 3 Change in the loss of cellulose material with time. Cellulase®(), Denimax Ultra L® (□ and O) and Cellusoft Ultra L® (∇). 1.5 gsamples of cotton cellulose from Wolff Walsrode were shaken (200 rpm) at50° C. and incubated with 2% (w/w, enzyme weight to cellulose weight)Cellulase® in 50 mM sodium acetate buffer having a pH value of 5.5. 1.5g cellulose samples were incubated under the same conditions with 6%(v/w, enzyme volume to cellulose weight) Cellusoft Ultra L®. Further 1.5g cellulose samples were shaken (200 rpm) at 60° C. and incubated with6% (□) and 15% (v/w) (O) Denimax Ultra L® in 50 mM potassium phosphatebuffer having a pH value of 7.0. The samples were removed at regularintervals and their wet and dry weights were determined in accordancewith FIG. 1. The losses of material were given as a percentage of theinitial weights.

FIG. 4 Change in the degree of polymerisation of the cellulose withtime. Cellulose samples were decomposed in the presence of variousconcentrations of the enzymes Cellulase® (), Denimax Ultra L® (□) andCellusoft Ultra L® (∇) according to FIG. 3; the samples were analysedand their respective degrees of polymerisation were determined.

FIG. 5 Change in the degree of substitution of enzymatically pretreatedcellulose derivatives in dependence on the enzyme concentration. Priorto the chemical conversion, the cellulose samples were pretreated withbuffer and various enzyme concentrations. Enzyme pretreatment of thesamples with (a) Cellulase® (), (b) Cellusoft Ultra L® (∇) and (c)Denimax Ultra L® (□) was carried out in accordance with the descriptionrelating to FIG. 1. Pretreated cellulose samples each having a weight of5 g and having water retention values of 2 g/g were then reactedchemically by incubation at 80° C., with shaking at 50 rpm, for 3 hoursin the presence of 50 ml of a mixture of dioxane and water (9:1) at amolar ratio of cellulose to propylene oxide of 1:5 and a molar ratio ofcellulose to 50% sodium hydroxide of 1:1.5. The degree of substitutionof the product was determined by means of solid-state NMR.

FIG. 6 Change in the degree of substitution of enzymatically pretreatedcellulose derivatives in dependence on the alkali concentration.Cellulose samples were pretreated with potassium phosphate buffer () orwith a concentration of 15% (v/w) Denimax Ultra L® (□) in accordancewith the description relating to FIG. 2. The pretreated samples eachhaving a weight of 5 g and having water retention values of 2 g/g werereacted chemically in accordance with the description relating to FIG.5, except that shaking was carried out at 200 rpm before and during thechemical conversion.

FIG. 7 Maximising the substitution of enzymatically pretreated cellulosederivatives by optimising the water content. Cellulose pretreated bypre-soaking in water (*), cellulose pretreated with buffer () andcellulose pretreated with Denimax Ultra L® (□) from Novo Nordisk. 5 gsamples of Temming 500 linters were shaken (200 rpm) at 60° C. andincubated for 2 hours in potassium phosphate buffer (50 mM, pH 7) withand without 6% (v/w--enzyme volume to cellulose weight) Denimax Ultra L®endoglucanase. Samples pretreated with water were incubated under thesame conditions in only water. After the incubation, the cellulosesamples were separated from the mixture and subjected to the chemicalconversion in accordance with the description relating to FIG. 5.

EXAMPLES Example 1

Enzymatic Pretreatment--Change in the Enzyme Concentration

The decomposition curves shown in FIG. 1 were used to calculate theinitial weights of cellulose required to prepare 5 g of pretreatedactivated cellulose substrate. Samples of commercial cotton cellulosehaving high crystallinity (>80%) and a degree of polymerisation ofapproximately 1500 were incubated at 36° C. with vigorous shaking (200rpm) for 20 hours in a suitable buffer in a ratio of cellulose to bufferof 1 g to 15 ml in the presence of various enzyme concentrations. Thesamples were incubated in 50 mM sodium acetate buffer at pH 5 withCellusoft Ultra L® concentrations of from 0 to 15% (v/w). Samplescontaining the same concentrations of Denimax Ultra L® were incubated in50 mM potassium phosphate buffer at pH 7.1. After the incubation, thesamples were cooled in an ice bath, filtered and washed under slightpressure using a no. 4 Buchner funnel. The pretreated samples havingequivalent dry weights of 5 g and water retention values of 2 g/g ofcellulose were then transferred to glass reaction vessels and subjectedto the chemical conversion process described in Example 2 below. Allstages of the pretreatment process were subjected to gravimetricanalysis and exhibited complete transformation of the material into thechemical conversion stage.

Example 2

Preparation of Hydroxypropylcellulose (HPC)

50 ml of a solution of dioxane and water (9:1) were added to thecellulose samples from Example 1 pretreated with endoglucanase. 50%sodium hydroxide and 100% propylene oxide were added to those mixturesin molar ratios of cellulose to substance of 1:1.5 and 1:5,respectively, and the contents were mixed by gentle slewing.

The samples were then reacted under pressure by reaction at 80° C. for aperiod of 3 hours with gentle shaking (50 rpm). The reacted samples wereremoved and left to cool for 5 minutes. The catalytic alkali wasneutralised by addition of 100% acetic acid in a molar ratio of 1:1. Thevolatile contents were removed by placing the reaction vessels in aslight air stream in a fume cupboard for 15 hours. The HPC was thenpurified by vigorous mixing with 200 ml of distilled water and dialysis(MWCO 1000) of the mixture for 5 hours under flowing distilled water andthen for 15 hours in a 2.5 liter water bath of distilled water at 4° C.The samples purified by dialysis were then dried in evaporating dishesunder dust-free conditions at 70° C. in a continuous low-pressurestream. The dried HPC samples were then comminuted by grinding at lowtemperatures and analysed by means of solid-state NMR. All stages of theprocess were subjected to gravimetric analysis and exhibited completetransformation of the material into the respective subsequent processstage. The NMR results were used quantitatively to calculate themolecular substitution (MS) and qualitatively to confirm the purity ofthe HPC. The results are shown in FIG. 5 and summarised below.

    ______________________________________                                                      Opt.   Loss of                                                     Conc. material  DP  MS                                                       Sample (%) (%) DP (%) MS (%)                                                ______________________________________                                        Sodium acetate buffer,                                                                      --     0       1475 100  0.41 100                                 pH 5                                                                          Potassium phosphate -- 0 1470 100 0.50 100                                    buffer, pH 7                                                                  Cellulase ® 4.0 9 1300 88.1 1.50 366                                      Endoglucanase - Cellusoft 6.6 0 1220 82.7 1.32 322                            Ultra L ®                                                                 Endoglucanase - Denimax  7.0 0 1360 92.5 1.05 201                             Ultra L ®                                                               ______________________________________                                    

Comparison Examples

For Examples 1 and 2, controls pretreated only with buffer and withoutenzyme were used. In addition, a commercially available cellulase fromMerck was also tested in a comparison. In that case, the cellulosesamples were pretreated by incubation at 36° C. and 200 rpm for 20 hoursin 50 mM sodium acetate buffer (pH 5) containing Cellulase®concentrations of from 0 to 15% (w/w).

Example 3

Enzymatic Pretreatment--Optimum Conditions

The decomposition curves shown in FIG. 3 were used to calculate theinitial weights required to prepare pretreated activated cellulosesamples having equivalent dry weights of 5 g. Samples of commercialcotton cellulose having high crystallinity (>80%) and a degree ofpolymerisation of approximately 1500 were incubated at 50° C. withvigorous shaking (200 rpm) for 2 hours in 50 mM sodium acetate buffer atpH 5.5 with a ratio of cellulose to buffer of 1 g to 15 ml in thepresence of a concentration of 6% (v/w) Cellusoft Ultra L®. Samplescontaining concentrations of 6% and 15% (v/w) Denimax Ultra L® wereincubated at 60° C. and 200 rpm for 2 hours in 50 mM potassium phosphatebuffer at pH 7.0. After the incubation, the samples were cooled in anice bath, filtered and washed under slight pressure using a no. 4Buchner funnel. The pretreated samples having equivalent dry weights of5 g and water retention values of approximately 2 g/g were thensubjected to the chemical conversion process described in Examples 4 and5 below. All stages of the pretreatment process were subjected togravimetric analysis and exhibited complete transformation of thematerial into the chemical conversion stage.

Example 4

Preparation of Hydroxypropylcellulose (HPC)

The cellulose from Example 3 pretreated with 6% (v/w) Denimax Ultra L®was subjected to the chemical conversion process described in Example 2,but with an important exception: 50% sodium hydroxide was added invariable molar ratios of cellulose to alkali of from 1:0 to 1:2.0. TheHPC was then purified according to Example 2 and analysed by means ofNMR. The results are shown in FIG. 6.

Example 5

Preparation of Hydroxypropylcellulose (HPC)

The cellulose from Example 3 pretreated with 15% (v/w) Denimax Ultra L®was subjected to the chemical conversion process described in Example 4,but with an important exception: the shaking speed during the chemicalconversion was raised to 200 rpm. The HPC was then purified according toExample 2 and analysed by means of NMR. The results are shown in FIG. 7.

For Examples 3, 4 and 5, controls pretreated only with buffer andwithout enzyme were used. In addition, a molar ratio of cellulose tosodium hydroxide of 1:0 in the chemical conversion yielded controls forthe required amount of catalytic alkali.

Example 6

5 g samples of commercial cotton cellulose (>80%, degree ofpolymerisation 1600) from Wolff Walsrode were incubated at 60° C. withincreased shaking (200 rpm) for 2 hours in buffer (pH 7, 50 mM) and inbuffer containing 15% (v/w--enzyme volume to cellulose weight) of theendoglucanase Denimax Ultra L® (Novo Nordisk). After the incubation, thecellulose samples were cooled in an ice bath and filtered under slightpressure. The wet weights of the samples were then measured and thewater retention values were calculated.

The samples were then reacted to hydroxypropylcellulose (HPC) byreaction at 80° C. for 3 hours with shaking at 200 rpm in the presenceof 30 ml of a mixture of dioxane and water (9:1) together with propyleneoxide and sodium hydroxide (50%) in molar ratios of cellulose toreactant of 1:5 and 1:1.5. After the reaction and subsequent cooling,the samples were neutralised by mixing with acetic acid (100%) in amolar ratio of acid to alkali of 1:1. The volatilising reactants wereremoved by placing in a slight air stream for approximately 15 hours.The HPC was then purified by the admixture of 200 ml of distilled waterand subsequent dialysis (MWCO 1000 dialysis tubes, Serva) first with acontinuous stream of water for 5 hours and then in 5 liters for 16 hoursat 4° C. The purified samples were dried in evaporating dishes underreduced pressure at 70° C. for 20 hours. The HPC samples were thencomminuted by grinding at low temperatures, before the MS values weredetermined by solid-state NMR. All stages of the process were subjectedto gravimetric analysis and exhibited complete transformation of thematerial into the respective subsequent process stage. The results aregiven in the Table below.

Example 7

Cellulose samples were pretreated by incubation in water, buffer orpuffer containing 6% (v/w) Denimax Ultra L® according to the descriptionin Example 6. Before the chemical conversion, distilled water was addedto the reaction mixtures in varying amounts. HPC was then prepared,purified and analysed according to Example 6. The results are shown inthe following Table and in FIG. 7.

    ______________________________________                                                           6%       15%                                                  Buf- Denimax Denimax                                                          fer Ultra L ®  Ultra L ®  Ex-                                      Change on conditions                                                                      MS Values        Increase                                                                              ample                                    ______________________________________                                        1) Chemical conver-                                                                       0.93   --       1.79    91%  2                                      sion with shaking                                                             at 200 rpm                                                                    2) Water content 1.7                                                          g/g of cellulose                                                              1) Chemical conver- 0.90 2.35 -- 161% 3                                       sion with shaking                                                             at 200 rpm Optimum                                                            water content                                                               ______________________________________                                    

What is claimed is:
 1. Process for the preparation ofhydroxyalkylcellulose ethers from the reaction of alkene oxides andactivated cellulose, characterised in that the cellulose is pretreatedas follows:a) incubation in a buffer solution or water or asolvent/buffer or water mixture and endoglucanase, b) separation of thecellulose pretreated with endoglucanase from the buffer or water orsolvent/buffer or water mixture, c) reaction of the activated celluloseto substituted cellulose derivatives by reaction with alkene oxides inthe presence of catalytic alkali.
 2. Process according to claim 1,characterized in that the endoglucanases are used from the groupconsisting of fungi, bacteria and plants.
 3. Process according to claim1, characterized in that the incubation is carried out at a temperatureof from 0° C. to 100° C. for a period of from 0.1 to 24 hours. 4.Process according to claim 1, characterised in that the incubation iscarried out in water or buffer or in a water/buffer or water mixturewith a buffer concentration in the aqueous phase of from 0 to 1000 mMand a pH value of from 1 to
 13. 5. Process according to claim 1,characterised in that the incubation is carried out with endoglucanaseenzyme in a concentration of from 0.01 to 50% of the weight of thecellulose.
 6. Process according to claim 1, characterised in that theincubation is carried out in the presence of a suitable concentration ofbiocides to prevent the growth of microorganisms and fungi.
 7. Theprocess of claim 2 wherein fungi are selected from the group consistingof Trichoderma reesei and Humicola insolens.
 8. The process of claim 2wherein bacteria are selected from the group consisting of Bacillus,Cellulomonas, Sprocytophaga, Cytophaga, Clostridium and Denimax UltraL®.
 9. The process of claim 3 wherein temperature is from 10° C. to 80°C.
 10. The process of claim 3 wherein temperature is from 50° C. to 60°C.
 11. The process of claim 3 wherein period is from 0.5 to 15 hours.12. The process of claim 3 wherein period is from 2 to 5 hours.
 13. Theprocess of claim 4 wherein concentration is 10 to 100 mM.
 14. Theprocess of claim 4 wherein concentration is 50 mM.
 15. The process ofclaim 4 wherein pH is 2 to
 10. 16. The process of claim 4 wherein pH isfrom 5 to 7.5.
 17. The process of claim 5 wherein concentration is 0.5to 30%.
 18. The process of claim 5 wherein concentration is 3 to 15%.